Coriolis

From GeoMod

A VPython model of a marble that can be fired across a rotating turntable. The trail of the marble's path across the turntable is traced behind it to show the Coriolis Effect. An application of the model in a large lecture class is described in the paper by Urbano and Houghton (2006).

There are links to excellent descriptions of what exactly is the coriolis effect (eg. Teunissen, 2007) and some of its history in the coriolis links section below.

Black and white rendering (for publication) of the coriolis effect as viewed from the perspective of the marble fired at the â€œTarget". Since the turntable is rotating, the marble will miss the intended target.

Multimedia

About

Like a number of 2-D Javascript applications available on the web, this model allows the user to fire a ball across a rotating disk, and marks its position relative to the disk and the general co-ordinate system. In this VPython model the user can also control the velocity of the ball, the angular velocity of the disk and the friction between the ball and the disk. This model is particularly useful in illustrating the effect of coriolis on atmospheric motion where these three parameters interact. A target can be placed on the disk to offer an objective of shooting the ball and to illustrate angular velocity. The model also permits the user to view the scene from the perspective of the ball, which has proven to be an extremely popular feature for all ages. This model and its application in a large lecture is described in Urbano and Houghton (2006).

NOTE: This model only accounts for the conservation of angular momentum component of the coriolis effect and not for conservation of linear momentum, which results in only half of the coriolis force (see Persson, 1998 for a good explanation).

Rotating disk viewed from above.

User's Guide: Model Controls

Cannon

Close view of cannon

Fire the marble by clicking on the marble atop the cannon.

Drag the cannon by its barrel to any position in the scene

Retreive the marble by clicking on the box (loader) of the cannon. (This leaves the marble trail on the turntable.)

Sliders

Velocity: Sets the speed of the marble.

Rotation: Sets the angular velocity and direction of rotation of the turntable.

Friction: Sets the degree of friction between the marble and the turntable.

Balls and buttons

Target: Rotates with the turntable when it is dragged onto the turntable. (Great for explaining angular velocity)

Reset All: Retreives the marble to the turntable and clears all trails off the turntable

Unmarked in the upper right: When this button is clicked it turns red and you see the scene from the marble's point of view. (Kids love this.)

Notes

Friction here only acts to drag the marble with the rotating turntable, and does not slow the marble speed (except if the rotation is moving the marble backward on the turntable).

This model only accounts for the conservation of angular momentum component of the coriolis effect, which gives only half of the effective coriolis force (see Persson, 1998).

Coriolis Links

There are a number of other sites that have excellent explanations of the coriolis effect, weather you need a simple description or a more in-depth analysis of the math. I've linked a subset of these below.